Reflectix Single Bubble Foil Question

[walhondingnashua]

As I am slowly finishing the inside of my garage (pole shed) I am working on the ceiling. The finished ceiling will be white interior grade steel with 1" of poly insulation that has 2 foil layers on each sheet. I will seal all the edges. Here is my question...

The builders used a layer of Reflectix single bubble wrap directly under the roof layer as a vapor barrier. There was a lot left over and I stapled what was left to the bottom of the trusses and it will between my ceiling steel and the insulation sheets. There was enough to do 3/5th of the ceiling. There are mixed opinions online about the benefits of this stuff. Is it worth it for me to buy more to finish the ceiling or am I just wasting money with the way I am insulating?

 

[festerw]

I didn't use the bubble foil but I used a radiant barrier sheet on the underside of my joists after retrofitting radiant heat.

It made a significant difference in the amount of heat coming into the basement and raised the floor temp 5 degrees.

I could see it helping with temps in the summer with proper roof venitlation.

 

[semipro]

There are mixed opinions online about the benefits of this stuff. Is it worth it for me to buy more to finish the ceiling or am I just wasting money with the way I am insulating?

While Reflectix might make a useful radiant barrier (only with a corresponding adjacent air gap) or vapor barrier, it doesn't provide much thermal insulation, not as much as they advertise anyway.
Your money is probably better spent on a dedicated radiant/vapor barrier.
The expert opinions on Reflextix aren't really that mixed. It's way overrated and overused.

Stay Away from Foil-Faced Bubble Wrap - GreenBuildingAdvisor

Foil-faced bubble wrap is not the insulation product it is often claimed to be. Its R-value is misrepresented and over-exaggerated.

www.greenbuildingadvisor.com

 

[snaple4]

the stuff works great compared to nothing. Correct me if I have this wrong; You have your ceiling Sheetrock, then ceiling joists, then layer of bubble, then space up to roof rafters, then bubble o top of roof rafters, then roof?

If no other insulation then the bubble stuff on top ceiling rafters will make all the air between the Sheetrock and bubble a layer of insulation (assuming it is properly sealed) that equals roughly R1/inch...

 

[ozarkoak]

the stuff works great compared to nothing. Correct me if I have this wrong; You have your ceiling Sheetrock, then ceiling joists, then layer of bubble, then space up to roof rafters, then bubble o top of roof rafters, then roof?

If no other insulation then the bubble stuff on top ceiling rafters will make all the air between the Sheetrock and bubble a layer of insulation (assuming it is properly sealed) that equals roughly R1/inch...

I used it in more of a radiant way. I lined my well house ceiling and walls. Usually a heat lamp was needed to prevent the well from freezing. Now the pressure tank which admittedly is large, provides enough warmth that the heater has not turned on this year.

 

[semipro]

the stuff works great compared to nothing.

Agreed, but you'd get 6 times the R-value from foil-covered polyiso foam board for the same money.

...If no other insulation then the bubble stuff on top ceiling rafters will make all the air between the Sheetrock and bubble a layer of insulation (assuming it is properly sealed) that equals roughly R1/inch...

An air space larger than about 1 in. loses effectiveness beyond R1 because of convective heat transfer within the space. If what you are saying was true no one would fill the space between their studs with insulation. They'd just seal up the sheathing and drywall.

 

[peakbagger]

Years ago I saw a demo that some college student did where he insulated a wall with sheets of plastic. He just filled the cavity with plastic sheets separated by 3/4" spacers. It was quite effective. He then went to 1" spacers and lost performance. I think he also did 1/2" spacers which had less of an impact.

 

[SpaceBus]

Years ago I saw a demo that some college student did where he insulated a wall with sheets of plastic. He just filled the cavity with plastic sheets separated by 3/4" spacers. It was quite effective. He then went to 1" spacers and lost performance. I think he also did 1/2" spacers which had less of an impact.

Sounds like a decent system for an animal house or maybe a heated shop.

 

[walhondingnashua]

The finished ceiling will be ribbed steel just like the exterior roofing and siding, but with white paint and no warranty. The main layer of insulation will come from 1" foil covered polyiso like the garage walls. I only put the bubble foil up because it was left over and didn't know if it was worth having more than 1 radiant barrier.

 

[Grizzerbear]

I have it under the metal siding and roof panels of my house. Shiny tin foil side facing towards the outside. It makes a hell of a difference on reflecting......not sure that's the word I'm looking for......heat away from the building. That said I dont think an extra layer for radiant purposes would increase the effectiveness much. It won't do much as far as insulating either but then again it certainly won't hurt.